stebbins



Nov. 29, 1927. 1,650,727

A. H. STEBBINS AIR CLASSIFIER Filed Sept. 28. 1926 Patented Nov. 29, i927.

more STATES retain PATENT "orrics.

ALBERT H. STEBBINS, DE LOS 'ANGELES, CALIFORNIA.

are oLAssIFrnn.

Application filed September 28, 1926. Serial No. 138,1d2.

treated repeatedly to the gentle separating action of slight air currents. Should it be attempted to effect a complete classification of line dust-like particles by a single air treatment the strength oi" the air employed would either fail to completely remove the line dust-like particles from the slightly larger particles or it would carry off many of the larger particles with the liner par ticles. 1

'ihe present invention therefore relates to an air classifier designed more particularly for use in the separation oiffine dust-like particles and which is provided with a plurality of classifying chambers arranged one above the other so that the materials that pass through one chamber are delivered to the next: for t 'irther treatment.

An important feature of the present invention resides in the construction whereby the material treating casing is divided into a plurality of chambers in each of which is provided a group of deflectors or screens arranged to tlis'eminate the materials and to retard their downward travel. within the casing so that, the materials are subjected to the classifying action of gentle currents of air within each chamber.

Another feature of the invention resides in theconstruction whereby the deflectors or screens are arranged to direct the materials back and forth from one side of the casing to the other as they pass downwardly therein.

Still another feature of the invention resides in a classifying casing having mounted therein a plurality of groups of screens formed of individual screens each of which provided with apertures that are large enough to permit the largest particles being treated to pass through the successive screens without lodging in the apertures.

Other features of tie invention and novel combination of parts in addition to the above will be hereinafter described in connection with the accompanying drawings, which illustrate one good practical form of the invention retreatment.

In the drawings-- Fig. 1 is a vertical sectional view through an air classifier constructed in accordance with the present invention big. 2 If; an edge view of Flg. 1 looking towards tne' right-hand edge thereof; and

Fig. 3 on a slightly enlarged scale is a sectional view taken on the line 33 of Fig. 1. The casing of the classifier forming the subject matter of the present invention preferably has a tower-like construction so that different classifying chambers may be formed in the casing one below the other, and the casing is preferably given more or less of a rectangular configuration in cross-section, as

will be apparent from Fig. 3 of the drawing,

so thatthe width of the casing between its side walls 10 is not very great. This is desirable because the air passing up through the screens within the casing can be better controlledin a narrow casing thanin a wide one as will be presently more fully pointed out;

The side walls 10 are connected by the end or edgewalls 11, and the upper end of the casing is closed by the cover 12, while the lower end of the casin is provided with and the'size of the opening .18 of the feed hopper through whichthe materials pass into the casing may be controlled by adjusting,

the sliding gate. 19.

Asstated, one of the features of the present invention resides: in the construction whereby the classifier'is provided with a plu rality of classifying. chambers disposed one below the other so'that the heavier materials may pass from one chamber to the next for The tower-like casingmay be ofsufiicient height to have any desirednumber of these classifying chambers formed therein, and inthe construction shownthe tower is provided with three separate chambers designated as A, B andC. These chambers are conveniently formedin the casing by providing the casing with an air inlet pipe or conduit 20 which extends across the casing in a downwardly inclined direction from one wall 11 thereof to a position near the oposite wall 11 sothat a relatively nar- Ill) seminating the materials delivered into each chamber and for retarding their progress downwardly through the chambers. may be done by providing a battle w1thin each chamber and each of these baflies may be constructed of a number ofscreensor defiectors. In the construction shown, eachof the chambers A, B and C is provided with a series of screens 22 which are supported in a downwardly inclined direction as shown, and the screens are positioned in close proximity to each other so that relatively narrow air passages are provided between them. The upper end of each screen is secured to or is disposed in close proximity to a wall 11 of the casing and the opposite sides of each screen may be secured to the side walls 10 of the casing. The widthof the casing from one wall 10 to the other should be relatively narrow because it is found that. the strength of the air currents passing upwardly through one or more narrow screens is much more uniform throughout the width ofthe screens than the strength of the air assin u vardl throu h wide screens.

It isimportant to note that these screens do not serve to grade or size the materials being treated, as in the case of the ordinary screen, but that their apertures are sufficiently large to permit the largest particles being treated within the casing to pass through the various screens without lodging in the apertures to clog the same. It will therefore be seen that the materials delivered into any one of the chambers will work downwardly through a number of the screens and will slide downwardly within the spaces 23 provided between these screens. In this manner the various particles are thoroughly disseminated and exposed to the action of the air passing upwardly through the screens.

The means for producing rising currents of airwithin the different chambers may be variously constructed, and in the embodiment of the invention shown air from the atmosphere or froma source of airpressure, such as a blastfan 24, is led into the chambers through apertures 25 formed in the upper face of thenir conduit 20 and these aperturesarepreferably provided with overhanging lips 26. which preventthe materials within the casing from entering the apertures 25; Each chamber A, B and C is preferably provided with an enlargement 27 formed at the edge of the casing lying opposite the delivery end of the inclined screens; this enlarged portion 27 is provided to form a passage between the ends of the screens and the edge wall ofthe casing adjacent the same, and also to form a space at one side of the casing adapted to receive This the suction pipe 28 which extends downwardly Within the casing. Each bulgin portion 27 is provided at its lower end wit 1 an inclined wall 29 which slopes downwardly in a direction to direct the materials into the discharge passage 21 above mentioned. The suction pipe 28 is provided with a slot 30 through which air is drawn into the exhaust pipe from the casing, and it should be noted that the slot 30 is formed in that wall of the pipe which faces away from the interior of the casing. This arrangement is desirable in order that the air will have to pass around they pipe 28 before entering the slot 20, thus giving the particles suspended in the air an opportunity to settle before they enter the slot 30. The materials that settle about the pipe. 28 will pass downwardly into the discharge pipe 31 and such materials as settle within the exhaust pipe 28 will escape through a small opening in the lower end of this pipe. The arrangement just described is such that air will pass upwardly through the screens 22, as will be apparent from the arrows, and will serve to carry upwardly through the screens into the upper portion of each chamber the liner particles. If desired one or more air inlet openings 33 may beprovided in an edge wall 11 of the casingto admit air into the casing adjacent the upper end of some of the screens. Each of the exhaust pipes 28 may be connected to a main pipe 3% which leads to the suction side of a fan As above indicated the air classifier form ing the subject matter of the present invention is particularly well adapted to classify very fine dust-like materials, and by providing a .large number of screens 22 in each chamber, the fine dust-like materials working downwardly through these screens will be thoroughly subjected to the action of the gentle air currents passing up through the apertures of the screens and through the air passages 23 between the adjacent screens. By arranging the classifying chambers in series one above the other so that the materials discharged from one chamber pass into the next for further treatment, the materialsymay be, treated over and over again until the desiredclassification effected. It will be noted that the screens 22 in the uppermost chamber A are arranged to direct the materials across the chamber to the left-hand side thereof, whereas the screens in the second chamber B serve to direct the materials in the opposite direction towards the right-hand side of the casing. In other words, the screens in the different chambers are given a zigzag arrangement so that they direct the materials back and forth across the casing as they pass clownwardly therein, more thoroughly to subject the materials to the action of the rising air currents.

llll) that is, claimed is 1. An air classifier for classifying line, dust-like particles, comprising in combination,"a tower-like casing, means for delivering the line, dust-like materials to be treatodto the upper part ot the casing, means for dividingthe casing into a plurality of classifying chambers arranged one above the other that the heavier particles 7 pass downwardly through the successive chambers, a group of deflectors mounted in each chamber to disseminate the materials and retard their downward travel therethrough, and means for producing currents of air within the chambers to carry off the lighter particles. i

2. An air classitier tor classifying line, dust-like particles, cor'nprising in combination, a tower-like casing, means for delivering the line, dust-like materials to be treat ed to the upper part oi the casing, means for dividing the casing into a plurality of classifying chambers arranged one ab ve the other so that the heavier particles pass downwardly through the succcss've chambers, a group of screens mounted within each chamber to retard the downward travel of the materials therein, and means for producing currents of air passing through the screens to carry oil the lighter particles.

3. An air classifier, comprising in combination,a tower-like casing, means for delivering the materials to be treated to the upper part of the casing, means for dividing the easing into a plurality of classifying chambers arranged one above the other so that the heavier particles pass downwardly through the successive chambers, a group of screens mounted within each chamber to disseminate the materials, and means for introducing air into each chamber below the screens and for exhausting the air from each chamber at a poiutabove the screens to carry oil the lighter particles.

4. An air classifier, comprising in combination, a tower-like casing, means for dividing the casing into a plurality of classifying chambers arranged one above the other so, that the heavier particles pass downwardly through the successive chambers, a group of deflectors mounted in each casing to dissemihate the materials and retard their downwardly through the successive chambers, a group of screens mounted in each chamber to retard the downward progress of the materials through the casing and having apertures that are large enough to permit the largest materials being treated to pass through the successive screens without lodging in the apertures, means for delivering the materials to be treated into the upper portion of the casing, and means 101 producing currents of air within the chambers to carry off the lighter particles.

(5. An air classifier for classifying line, dust-like particles, comprising in combination, a casing, means for delivering the line, dust-like materials to be treated into the upper part of the casing, a plurality of groups or screens mounted in the casing to direct the materials back and forth from one side of the casing to the other as they pass downwardly within the casing, each group of screens being termed of a series oi screens mounted one below the other and provided with apertures that are large enough to permit. the largest particles bemg treated to pass through the successive screens without lodging in the apertures, and means for producing currents of air within the casing to carry oil the lightestparticles. 7

7. An air classifier, comprising in combination, a tower-like casing, means for de livering the materials to be treated to the upper part of the casing, means for dividing the casing into a plurality oi classifying chambers arranged one above the other so that the heavier'particles pass downwardly through the successive chambers, a group of battles mounted in each chamber to retard the progress of the materials downward through thechamber and arranged to pro vice a spaceabove the battles inwhich the particles within the air may settle, and means tor passing air upwardly throughthe battles I o. An an classihei, comprising 111 combination, a tower-like casing, means for de livering the materials to be treated to the upper part of the casing,-means for divid ing the casing into a plurality of classifying chambers arranged one above the other so that the heavier particles pass downwardly through the successive chambers, a group of battles mounted in each chamber to retard the progress of the n'iaterials downward through the chamber, and means for ex hausting the air from each chamber comprising an exhaust pipe extending downwardly within the chamber at one side thereof and having an air inlet slot formed in the Wall of the pipe that faces away from the central portion of the casing.

9. An air classifier for classifying fine, dust-like particles, comprising in combination, a casing, means for delivering the finedust-like materials to be treated into the up per portion of the casing to pass down wardly therein, a series of inclined screens mounted in the casing one above the other in close proximity to each other to retard the downward passage of the materials within the casing and having apertures that are large enough to permit the largest materials being treated to pass through the suc cessive screens without lodging in the apertures, and means for producing currents of air passing upwardly through the inclined screens in opposition to the falling materials and of sufficient strength to pick up the finer but not the coarser dust-like particles.

10. An air classifier for classifying finedust like particles, comprising in combination, a casing, means for delivering the fine, dust-like materials to be treated into the upper portion of the casing to pass downwardly therein, a series of screens mounted in the casing in close proximity to each other and at a steep inclination to. retard the downward passage of the materials within the casing and to form narrow steeply inclined air passages between the adjacent screens, said screens being provided with apertures that are large enough to permit the largest particles being. treated to pass through the successive screens without lodging in the apertures, and means for producing currents of air passing upwardly through the inclined screens in opposition to the falling materials and of sufiicient strength to carry off the finer but not the coarser dust-like particles.

11. An air classifier for classifying fine, dust-like particles, comprising in combination, a tower-like casing, several'groups of deflector surfaces arranged within the casing in zigzag relation so that the materials being treated are directed alternately back and forth across the receptacle by the sucessive groups of deflectors, each of said groups comprising a series of similarly inclined apertured surfaces through which the materials to be treated may pass in opposition to rising air currents, means for delivering the fine-dust-like materials to be treated to the upper part of the casing, and means for producing rising currents of air passing upwardly through the apertured surfaces in opposition to the falling materials to carry off the lighter particles.

12. An air classifier for classifying finedust-like particles, comprising in combination, a tower-dike casing, several groups of screens mounted within the casing in zigzag relation to direct the materials being treated alternately back and forth across the casing and. each group consisting of a series of similarly inclined screens disposed in ciose relation to form narrow air passages between them, means for'delivering the finedust-like materials to be treated to the upper part of the casing, and means for producing rising currents of air passing upwardly through the screens in opposition to the falling materials to carry ofi'the lighter particles.

13. An air classifier for classifying finedust-like particles, comprising in combination, a casing, means for delivering the fine dust-like materials to be treated into the upper part of the casing to pass downwardly therein under the influence of gravity, a plurality of oppositely inclined baffles mounted in the casing in zigzag relation to direct the materials back and forth across the casing, each baffle consistingof a group of similarly inclined deflector surfaces arran ed to provide air passages between them, and means for producing currents of air passing upwardly between the deflector surfaces in opposition to the falling materials to carry off the lighter particles.

In testimony whereof, I have signed my name to this specification.

ALBERT H. STEBBINS. 

